Referring to FIG. 1, a conventional cutter for a wood planing machine, as disclosed in U.S. Pat. No. 4,538,655, includes a rotary shaft 11 extending along a longitudinal direction and rotatable about an axis, a plurality of cutting strips 12 and a plurality of fasteners 13. The cutting strips 12 are elongated, are parallel to the axis, and are circumferentially disposed on the shaft 11. The fasteners 13 respectively fix the cutting strips 12 on the shaft 11.
During the planing process, the whole piece of each cutting strip 12 is in contact with a to-be-planed surface of a workpiece. Because a contact area between each cutting strip 12 and the to-be-planed surface of the workpiece is large, when the shaft rotates in high speed, each cutting strip 12 imposes a high impact against the to-be-planed surface. Aside from producing a large sound or noise, because the resistance is large, a huge amount of energy is consumed, so that the work efficiency is reduced. Further, each cutting strip 12 is easily damaged.
FIG. 2 illustrates another conventional cutter of a wood planing machine. The conventional cutter includes a rotary shaft 21, a plurality of cutting blades 22 and a plurality of fasteners 23. The shaft includes a plurality of circumferentially spaced-apart spiral side surfaces 211 extending along a longitudinal direction. The cutting blades 22 are disposed on the spiral side surfaces 211. Each fastener 23 extends through a respective one of the cutting blades 22 and engages a corresponding spiral side surface 211 to thereby fix each cutting blade 22 on the shaft 3.
The cutting blades 22 are small in size and are disposed in the spiral side surfaces 211 of the shaft 21. Thus, a contact area between the cutting blades 22 and a to-be-planed surface of a workpiece is reduced. After each cutting blade 22 planes a small region of the to-be-planed surface, a next one of the cutting blades 22 continues the planing process. This can effectively decrease the noise and the resistance produced during planing of the to-be-planed surface of the workpiece. However, because the shaft 21 needs to go through a fine processing so that the side surfaces 211 thereof extend in a spiral manner, and because the cutting blades 22 are small in size so that it is difficult to manufacture and process the same, a high investment is thus required for the manufacture and process of the shaft 21 and the cutting blades 22.